time-nuts@lists.febo.com

Discussion of precise time and frequency measurement

View all threads

sine to square wave circuits - performance data?

MS
Mark Sims
Wed, Oct 4, 2017 11:36 PM

The second LPRO circuit uses a feedback resistor across an inverter... I used to make oscillators that way... I'm not sure how that works out for a squarer.  They call it a "self-biased" squarer.

My input gate is a 74HC86.  It is normally configured as a buffer so a feedback resistor would add some hysteresis.  With the HC86 configured as an inverter, it would be like the second LPRO circuit.

I've seen these single gate squarers built with '04s and '14s.  If you have a crappy input signal the hysteresis of the '14 could add more goodness than the increased noise from hysteresis takes away.

The second LPRO circuit uses a feedback resistor across an inverter... I used to make oscillators that way... I'm not sure how that works out for a squarer. They call it a "self-biased" squarer. My input gate is a 74HC86. It is normally configured as a buffer so a feedback resistor would add some hysteresis. With the HC86 configured as an inverter, it would be like the second LPRO circuit. I've seen these single gate squarers built with '04s and '14s. If you have a crappy input signal the hysteresis of the '14 could add more goodness than the increased noise from hysteresis takes away.